Learn what words mean. That comment is not remotely condescending, and scribbling in one's own book (with no indication here that the owner intends to sell it) is not vandalism.
Oh, I recognize your name ... wrong about so many things.
From another one of your comments here:
> No, my argument is that it's totally obnoxious to lend or resell a book that you've written in
But the person who advocated for writing in one's books if desired said nothing about lending or reselling them ... YOU were the first person here, in your response to them, to whine about BUYING such books. Talk about obnoxious!